<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
   
  </head>
  <body>
    <div id="app">
      <button @click="addArr">新增li</button>
      <ul id="oul">
        <li v-for="item in arr" :key="item">
          {{item}}
        </li>
      </ul>
    </div>

    <script src="./vue.global.js"></script>
    <script>
      const { createApp } = Vue;
      const app = createApp({
        data() {
          return {
            arr: [1,2,3,4]
          };
        },
        methods: {
          addArr(){
            
            const oul = document.querySelector('#oul');
            this.arr.push(this.arr.length+1);
          }
        },
      });
      app.mount("#app");
    </script>
  </body>
</html>
